1. Field of the Invention
The invention relates to a plastic mold which is suitable for the production of latex foam moldings (molded articles) by means of microwave energy. Economic and production engineering advantages are achieved by the use of the mold according to the invention.
2. Discussion of the Background
The production of latex foam molded articles, such as for example, mattresses and cushions, is currently still carried out exclusively in metal molds, which are heated directly by heating fluid or steam. The use of microwave energy demands the use of nonmetallic molds. The production of latex foam moldings by means of microwave energy is described in DE-OS 39 00 809. The proposed mold materials are materials having a thermal conductivity of less than 1 W/m.times.K, such as for example, polysulphone, polycarbonate, polytetrafluoroethylene, polyethylene and polypropylene.
As experiments have shown, the plastics mentioned in DE-OS 39 00 809 are, however, not suitable for the production of large molds, such as for example, for mattresses. At practicable wall thicknesses, polyethylene, polypropylene and polytetrafluoroethylene have too low a rigidity and thus mold stability, which leads to the molded articles having inadequate dimensional accuracy.
Under continual exposure to alternating temperatures when filling the hot mold with cold latex foam, and under the influence of moisture, alkali, residual monomers, vulcanizing agents and their decomposition products and the mechanical stress on the mold, for example when releasing the articles from the mold, polycarbonate and polysulphone show stress cracks after a short time.
R. Ostwald and A. F. Bogenschuetz, Kunststoffe (1988), 78 (6), pages 499 to 504, describe the use of films which can be composed of polyphenylene ether, as a polymer anticorrosion coating for high-frequency components.
Foamed foodstuff packaging materials, composed of molding compositions based on polyphenylene ether, for use in microwave ovens are described in EP-A-0 325 779 and EP-A-0 377 115.